Apple, Mac, OS X 10.9 (Mavericks): Reinstall OS X System

1. Restart System
To restart OS X 10.9 (Mavericks) system choose Apple menu > Restart

2. Recovery Mode
When your Mac restart and the gray screen appears hold down the Command (⌘) and R keys.

3. Choose the Wi-Fi
Choose a network from the Wi-Fi menu (in the top-right corner of the screen)

4. Reinstall System
Select Reinstall OS X, then click Continue.

5. Select Disk
Select your current OS X disk (in most cases, it’s the only one available).